The invention described and claimed herein is generally related to hand-held power tools. In particular, the present invention is related to hand-held power wrenches.
Power tools are virtually indispensable to auto mechanics and others in the field of auto repair and other medium duty mechanical applications. Speed of assembly and disassembly is an essential requirement that dictates the use of such power tools. However, the development of power tools, particularly power wrenches, has not kept pace with the development of automobile engine systems, which have evolved toward increasingly complex and closely packed engine systems. As a result of the increasing number of components in the modern automobile engine, disassembly and subsequent reassembly of the components which must be removed to gain access to a desired component has become an increasingly greater part of any repair or servicing of a vehicle. As a rule, commercially available power wrenches have remained the same size for approximately two decades, while engine compartments have become increasingly smaller and complex. Accordingly, while the need for power wrenches has steadily increased, their utility has to some extent declined because they are increasingly impractical to use in the tight spaces of a modern engine compartment.
Contemporary power wrenches are exemplified by the wrenches disclosed in U.S. Pat. No. 4,346,630 to Hanson, issued Aug. 31, 1982, and U.S. Pat. No. 3,529,498 to Northcutt, issued Sept. 22, 1970. Each of these patents discloses a power wrench having an angularly reciprocating, or oscillating, ratchet head that drives a rotatable square drive socket wrench stud. Standard wrench sockets are emplaced on the stud and driven either clockwise or counterclockwise, with the direction of rotation being selected by means of a bidirectional pawl and ratchet assembly.
A primary disadvantage of many of the commercially available power wrenches is that the direction changing mechanism is typically located on the back side of the wrench head, on the opposite side from the square drive stud where a socket is located. This results in the head of the wrench being relatively thick, thereby limiting its use in close quarters where there is little head room. Also, it can result in a serious problem if, while unscrewing a bolt or while removing a nut from a stud, the wrench head is inadvertently allowed to be driven backwards against a solid obstruction. In such an event the direction changing mechanism, being located on the back side of the wrench, becomes jammed against the obstruction. Because of the high torque applied by the drive motor, the wrench can suddenly become so jammed that the direction adjustment mechanism cannot be turned, or even reached, to reverse the direction of the wrench and thereby release the wrench from the jammed position. If the wrench is allowed to be jammed into such a position, it can be virtually impossible to remove the wrench without extensive and sometimes destructive disassembly of surrounding components, to remove the obstruction and thereby release the wrench.
Another disadvantage of commercially available power wrenches such as those described above follows from the fact that they typically include a standard square drive socket wrench stud, to which must be attached a standard closed end socket. Closed end sockets are those which are closed at one end and which therefore have a central bore of only a limited depth, typically less than about two inches at most. As a result, the commercially available power wrenches, with their associated closed end sockets, cannot be used to turn nuts on long studs or bolts. Such nuts must ordinarily be turned manually with hand-held open end or box end wrenches.
Another disadvantage of the previously known power wrenches is that they must typically be removed from a workpiece in order to actuate the direction changing mechanism, particularly when they are positioned on a nut or bolt that is hard to reach or when the wrench is in such a position that it can only be accessed with one hand. This difficulty occurs because the direction changing mechanism, when located on the back side of the wrench head, is difficult to reach with the same hand used to hold the wrench by its handle. At best the direction changing mechanism cannot be reached easily, and often the wrench cannot be released to access the direction changing mechanism, even momentarily, without the wrench falling off the workpiece.
Accordingly, it is an object and purpose of the present invention to provide an improved power driven wrench.
It is also an object of the present invention to provide an efficient and reliable power wrench that is a box end wrench.
It is another object of the present invention to provide a power driven box end wrench that is sufficiently compact to permit its use in tight spaces, and which is sufficiently thin in profile that it requires less head room than is required of previously known power wrenches.
It is yet another object of the present invention to provide a power driven wrench which has a direction changing mechanism that is not located on the back side of the wrench head.
Another object of the invention is to provide a power wrench that has a direction changing mechanism that can be manipulated with the same hand used to hold the wrench, without having to let go of the wrench.
Another object of the invention is to provide a power box end wrench which can be changed in direction without the necessity of removing the wrench from a workpiece.